1. Field of the Invention
The present invention relates to a voltage error correction system, and particularly to a system for correcting errors generated by a voltage generator.
2. Description of Related Art
A power supply system is usually used for receiving an alternating current (AC) voltage, and converting the AC voltage into a positive voltage by a positive direct current (DC) voltage generated by a voltage generator which has errors. Then, the positive voltage is converted into a digital voltage provided to a digital electronic device.
Referring to FIG. 2, one such power supply system, such as a motor driven power supply system, includes a voltage generator 10, a voltage converter 20, and an analog to digital converter 30. The voltage converter 20 receives an AC voltage Vin provided by a power supply (not shown), and a positive DC reference voltage Vref provided by the voltage generator 10. The voltage converter 20 is configured for adjusting the AC voltage Vin proportionally, adding the adjusted AC voltage Vin to the reference voltage Vref to obtain a positive voltage, and outputting the positive voltage to the analog to digital converter 30. The analog to digital converter 30 receives the positive output voltage from the voltage converter 20, and converts the positive voltage into a digital output voltage Vout.
In this power supply system, if an error exists in the reference voltage Vref provided by the voltage generator 10, the system takes no error correction measures, thereby the error still exists in the digital voltage Vout. For example, if the range of the AC voltage Vin is from −2.0 volts to +2.0 volts, an adjustment ratio of the voltage converter 20 is predetermined to be 0.75. When the voltage generator 10 outputs an 1.6 volt reference voltage Vref (which has an 0.1 volt absolute error), the voltage converter 20 adjusts the AC voltage Vin proportionally and adds the reference voltage Vref to the adjusted AC voltage Vin, and the range of the output voltage from the voltage converter 20 is from −2.0*0.75+1.6=0.1 volts to +2.0*0.75+1.6=3.1 volts. The range of the output voltage from the analog to digital converter 30 is 0.1-3.1 volts. That is to say, the 0.1 volt absolute error still exists in this power supply system.
Therefore, it is desired to provide a voltage error correction system to overcome the above described shortcomings.